The present invention relates to methods for bridging the joint between wall board panels in general, and to methods for bridging the joint in structures subject to later flexing or distortion in particular.
In modern commercial and residential construction interior wall surfaces are typically formed from flat modular units affixed to wood or metal studs. These units, know as sheet rock, gypsum board, plasterboard or generically herein as wall board, come in standard dimensions which are abutted to form a continuous surface. In order to present a surface which is unmarked by visible seams, it is necessary to position bridging tape which overlaps the joint and which supports a coating of a wet plaster-like compound known as mud. The mud is applied to obscure any variations in the wall profile, and to form the wall surface into an uninterrupted expanse.
Conventional drywall tape is typically a simple perforated kraft paper strip which is adhered to the drywall surfaces by a coating of mud. Because the mud must be applied as the tape is positioned, operators must take care not to discharge the mud onto non-work surfaces. In addition, once the drywall tape has been applied an installer must wait as much as a day for the mud to dry before a final surface coat of mud can be applied.
In the manufactured housing industry, however, houses of modular dimensions are assembled on an assembly-line as part of an ongoing process. Whereas in conventional site built housing, the structure of the house, including all framing and truss work, is completed before drywall is attached, in manufactured housing subassemblies comprised of roof trusses and drywall forming a ceiling are prepared and transported into place on the structure's walls. This displacement and transportation of a drywall ceiling assembly after it has been taped and mudded subjects the drywall joints to racking and twisting which may immediately cause cracking at the joints, or may induce cracks to appear at a later time. Cracked ceilings are unacceptable to the purchaser of a new manufactured home and impose significant costs on the manufacturer for on-site visits to manually repair the cracks.
Gypsum-based mud dries to a brittle substance. Although this dried mud is readily sanded or painted, it is also susceptible to cracking when subjected to racking and twisting. Flexible joint compounds are known which rapidly form a skin which can be painted, while the interior of the applied flexible joint compound remains soft and un-cured. However, the portions which dry are extremely hard and are not readily sanded. Conventional self-adhesive drywall tapes such as mesh tape, and the tape disclosed in U.S. Pat. No. 5,246,775 to Loscuito, have a multitude of screen openings or perforations which, when penetrated by the flexible joint compound act to extrude a multitude of tiny protrusions which significantly compromise the smooth surface of the ceiling.
What is needed is a method for bridging the seams between adjacent ceiling or wall boards and a manner which permits immediate painting and finishing yet which is tolerant of subsequent displacement.